BEIJING — China's trade with North Korea fell sharply in September as sanctions finally began to bite, data released by the Chinese government Friday showed.

China says it has implemented successive rounds of sanctions, agreed to by the U.N. Security Council, that are meant to pressure Pyongyang to abandon its nuclear and ballistic missile programs. China is North Korea's economic lifeline, and Beijing's role in the sanctions effort is critical.

On Friday, China's General Administration of Customs announced that China's imports from North Korea fell 37.9 percent in September, the seventh successive monthly decline. China's exports to North Korea dropped a more modest 6.7 percent in September, Huang Songping, spokesman for the customs department, said at a news conference.

Although there is room for considerable skepticism about official Chinese data — and the numbers can swing wildly month to month — there is reason to believe that there has been a recent slowdown in trade, experts say.

Chinese traders in the border city of Dandong told The Washington Post this month that they were feeling the effect of the sanctions, which were being imposed with unprecedented determination by the authorities.

Nevertheless, fishermen and seafood traders said smuggled seafood was still moving across the border.

Successive rounds of U.N. sanctions have cut off more than 90 percent of North Korea's publicly reported exports — including coal, iron ore, seafood and, most recently, textiles — and have restricted the regime's ability to earn foreign currency by sending workers abroad.

China accounts for roughly 85 percent of North Korea's external trade and is seen by many as the key to forcing Pyongyang to at least freeze its nuclear and missile programs. But China has balked at imposing a complete trade embargo on North Korea, and continues to send the regime the crude oil it needs to keep its military and economy alive.

North Korea's deficit with China more than tripled in the first nine months of the year from the same period in 2016, to $1.07 billion, Huang told a news conference, according to Bloomberg News.

There are no records of seafood imports from North Korea, Huang said, while shipments of coal, iron ore and clothing all declined.